Polymerization method



Patented Nov. 9, 1943 I@UNIT ED STATES PATENT OFFICE POLYMERIZATION METHOD Edgar o. Britton and Walter J. Le Fem, Midland, b., assignors to The Dow Chemical 1 Company, Midland, Mich a corporation of Michigan No Drawing. Application August 3, 1940,

Serial No. 351,223 I r 13 Claims. '(ci. etc-as) gredients in promoting the polymerization of vinyl compounds, but it is pointed out that, in

' order to obtain best results when using the complex catalysts, other polymerizing conditions must be varied to suit the particular vinyl compound under treatment Said co-pending application acknowledges that the present applicants have invented improved methods of employing the complex catalysts for the polymerization of certain unsaturated organic compounds.

In our studies 01 the above-mentioned complex catalysts, we have found that, although they are exceptionally efiective in promoting the polymerization of a wide variety of polymerizable organic compounds, the efiectiveness oi the catalysts is largely dependent upon the particular combination oi polymerizable compound and reaction medium employed, 1. e. a medium best suited to polymerization of a given unsaturated organic compound with the catalyst frequently interferes with the polymerization of a difierent unsaturated organic compound with the same catalyst. For instance, in polymerizing vinyl cyanide with such complex catalyst we have found that the catalytic polymerization occurs rapidly when aqueous methanol is used as a medium, but that it takes place sluggishly if carried out in aqueous emulsion. In contrast, the polymerization of vinylidene chloride, 1. e. assym.- dichloro-ethylene, with the complex catalyst occurs rapidly it carried out in aqueous emulsion, but only sluggishly ii attempted in aqueous methanol solution. The cause of this phenomenon is not known.

We have further found that, when using the new complex catalysts for the polymerization of unsaturated organic compounds having the general formula,

wherein X represents hydrogen, halogen or an alkyl substituent and Y represents a halogen, an alkyl-carbonyl, an alkoxy-carbonyl or an acyloxy substituent, and the compound contains halogen only when X and Y both represent halogen, the polymerization takes place most rapidly and completely ii carried out in aqueous emulsion. As hereinbeiore stated, such is not the case when using the same catalyst for the polymerization of other polymerizable unsaturated organic com- Eiitlmples of the unsaturated organic compounds having the above general formula which may advantageously be polymerized in aqueous emulsion using the new'complex catalysts are vinylidene chloride, vinylidene bromide, vinylidene chloro-bromide, methyl 'acrylate, ethyl acrylate, methyl methacrylate, ethyl methacryllate, methyl alpha-ethyl acrylate, methyl vinyl ketone, ethyl vinyl ketone, methyl alpha-methylvinyl ketone, vinyl acetate, vinyl propionate, etc.

As hereinbeiore indicated, the complex catalysts employed to promote the polymerization comprise as their essential ingredients an acid, a

per-oxygen compound capable of supplying nascent oxygen in the reaction mixture, and a ferric compound. The kinds and the proportions of acid, per-omgen compound and ferric commund employed as catalyst ingredient may be varied widely. Any water-soluble acid of strength suflicient to render the emulsified reaction mixture definitely acidic may be used as the acid ingredient. Examples of such acids are nitric acid, hydrochloric acid, sulphuric acid, benzene sulphonic acid, acetic acid, chloroacetic acid,

etc. The acid is employed in amount sufllcient to reduce the pI-I. value oi the emulsion to below avoid possible hydrolysis.

6, and preferably to between 1.5 and 3. Best results are usually obtained'when employing nitric acid in the proportions just stated as the acid ingredient of the catalyst, althoughin polymerizing readily hydrolyzable organic compounds, e. g. vinyl acetate or other vinyl ester, a weaker acid such as acetic acid is preferably used so as to mole of the organic compound to be polymerized,- but it may be used in other proportions 1! desired.

Examples of ferric compounds which may be It may, of course. be carried out at temperatures up to the decomposition point or the product, e. a. at 150 C. or higher. Air is preferably excluded during the polymerization, e. g. by carryemployed as catalyst ingredients are ferric ni- 5 ing the reaction out in a closed container or in trate, ferric chloride, ferric sulphate, ferric ace- Contact with it bo d or other tate, ferric salts of sulphonic acids such as beninert gas, S c molecular y en. if absorbed in zene sulphonic acid, toluene sulphonic acid, sullarge qu y, may Cause discoloration of the phonated sperm oil, etc. Apparently any ferric Product. The polymerization may usually be compound which is soluble or emulsifiable it completed within 10 hours and in some instances water may b employed, Th rti of ferric may be carried to completion within one hour. compound is preferably very small, between The mixture is preferably agitated during the 0.0001 and 0.05 per cent by weight of iron relative P ymerization. to the vinyl compound usually being employed, After completing the po iz n, the 8111111" although smaller or somewhat larger proportions l5 sion is broken in any of the usual ways. 8. g. y may be d, heating the same or by adding methyl alcohol, It will be noted from the foregoing statements ethyl alcohol, D p l. acetone, ammonia. that the proportions of the several catalyst inor y adding salts such as sodium chloride, calgredients with respect to one another may be oium chloride, whereby the p m r or varied over wide ranges. However, we usually ym r i pr ipitated, lly as a Powder. employ the ferric compound and the peroxide in The p ec pitate is separated, washed free of adrelative proportions corresponding to between hering mother-liquor. and dried- The yield o about 0.000001 and 0.0004 gram atom of iron po ymer from the method lust described is usually per mole of the peroxide. As hereinbefore stated, high; i Some instances q t tive. the acid is advantageously used in amount sufil- The following examples describe a number of cient to lower the pH value of the reaction mix- Ways in which th pr ciple of the invention has ture to below 6 and preferably to between 1.5 been p t y e t to e construed as and 3. limiting the invention.

In preparing the emulsified reaction mixture, the polymerizable organic compound and the es- EXAMPLE 1 sential catalyst ingredients in the proportions hereinbefore stated are mixed in any desired or- Each of a number, of pQlymenzable organic der with water and an l if i agent and compounds was emulsified with water: as follows: the mixture is agitated to effect emulsification. 25 parts by weight of the polymenzable The identity of the emulsifying agent is of secpound, parts of a (mute aqueous hydrogen ondary importance provided of course that it peroxide solution (contalning 75 parts of water is one forming stable emulsions with the acidic and part 0f hydrogen peroxide) and Parts mixture required by the invention. A number of NOD60 sodlum Salt f Su1phnated sperm emulsifying agents having the property of form 011). were mixed and the m xture was agitated ing stable emulsions of organic compounds with 40 1mm emulslfied- The emulslon was dlvlded Into dilute aqueous acids are known. Among the vari- 3 poljtions and one was treated Wlth an Gus mul ifying agents which may be used are acid in amount sufficient to reduce its pH value egg albumen and alkali metal. sulphonates of to 2, and another portion was treated a, aliphatic or alkyLa -omatic hydrocarbons of high proportion of the acid and also with ferric chlomolecular weight. NOD00 (a Sodium salt of ride in amount corresponding to 0.004 per cent phonated sperm oil) is particularly well adapted of the Weight of the mixturee three Samples to u e as the agent The proportion Of the emulsion were then maintained at a temof emulsifying agent required is usually small, perature of 40 C. in closed containers for the e Nopco when used is preferably emplgyed time stated in the following table, after which i amount corresponding to between (L1 and each Sample was treated methanol to preper cent of the weight of the water. pi the Polymer and the yield of p l m r The emulsion is brought to a temperature was determined. The following table names the ficient to cause rapid polymerization of the unpoiymerizable organi mpound subjected to saturated organic compound, the preferred temeach test. States which f h C talyst inperature being dependent upon t particular gredients, hydrogen peroxide, acid, and ferric polymerizable compound under treatment, In chloride was present in the emulsion subjected to most instances the polymerization occurs rapidly w gives the e over which, each land smoothly at temperatures between 20 and 51011 was maintained at and gives the 100 C., and in some instances it may be carried De cent yield of p ymer, based on the amount out rapidly at temperatures as low as 10 c. o p ymerizable org nic compound employed.

Table I Time Polymer Run No. Polymerizable compound Catalyst ingredients hours pgriecfiit i" :8;+HNO fi 3-- n Hz0 +HNOa+FeCh 6.75 40.0 4-- Vinyl H 0 10 13. 2 5 do H 0 +acetic acid 10 Trace (L dn He0g+acetlc acid+FeC1a 10 28.2 7 Methyl methacrylate. H 00 7 None g (In 7 None 1; 15 Ti er: ii liiii HZoilfiixidJIIIL- 14:5 2.2 12 do H,0,+HNO,+Fecir 14.5 as

.. assaoss 3 From the data in Table I it will be seen that rated organic compound having the general forthe catalytic mixtures oi peroxide, acid and formula. 1 ric compound were far more active than either x the peroxide alone or the mixtures of peroxide H and acid in promoting the polymerization. 5 y

An emulsion of vinyl acetate,'which emulsion contained hydrogen peroxide, acetic acid and ferric chloride and had the same composition as that employed in run 6 of Table I, was prepared as in Example 1. The emulsion was heated in a closed container at a. temperature of 50 C. for hours, after which it was treated with methanol to precipitate the polymer. The latter was separated from the mixture, washed with water, dried and weighted. The yield ofsolid polymerized vinyl acetate was quantitative.

Other modes of applying the principle of the invention may he employed instead or those explained, change being made as regards the method herein disclosed, provided the step or steps stated wherein X represents a substituent selected from the group consisting of hydrogen, halogen and alkyl substituents and Y represents a substit uent selected from the group consisting of halogen, alkyl-carbonyl, alkoxy-carbonyl, and alkyl-.

carbonyl-oxy substituents, and the unsaturated organic compound contains halogen only when X and Y both represent halogen, the stepsof forming an aqueous emulsion of the unsaturated organic compound, which emulsion also contains, as ingredients of the emulsion, small proportions of a water-soluble acid, a per-oxygen compound, and a ferric compound, and polymerizing the unsaturated-organic compound while in said emulsion.

2. In a method for polymerizing an unsaturated organic compound having the general formula,

wherein X represents a substituent selected from the group consisting of hydrogen, halogen and alkyl substituents and Y represents a substituent selected fromthe group consisting of halogen, alkyl-carbonyl and alkoxy-carbonyl and alkylcarbonyl-oxy substituents, and the unsaturated organic compound contains halogen only when X and Y both represent halogen, the steps of forming an aqueous emulsion of said unsaturated organic compound, which emulsion contains, as ingredients thereof, a water-soluble acid in amount suillcient to reduce the pH value of the emulsion to below 6, a ferric compound in amount such that its iron content corresponds to between 0.0001 and 0.05 per cent of the weight of the unsaturated organic compound, and between 0.002 and 0.2 mole of a peroxide per mole of the unsaturated organic compound, and polymerizing the unsaturated organic compound while in said emulsion.

3. In a method for polymerizing an unsatuwherein X represents a'substituent selected from the group consisting oi'hydrogen, halogen and alkyl suhstituents and Y represents a suostituent 'X and Y both represent halogen, the steps of forming an aqueous emulsion of said unsaturated organic compound, which emulsion contains, as idients thereof, a water-soluble acid in cunt sumcient to reduce the pH value of the emulsion to hetween 1.5 and 3, a ferric compound in amount such that its iron content corresponds to between occur and 0.05 percentof the weight of the unsaturated organic compound, and betwe 9.902 and 0.2'mole of hydrogen peroxide per mole of the aturated organic compound, g th 1:. turated organic compound while in said emulsion, and thereafter precip itating and separating the polymer. 7

4. In a method ior polymerimng an unsaturated orgc compound having the general forthe group consisting of hydrogen, halogen'and alkyl substituents and Y represents a substituent selected from the group consisting of halogen,

alkyl-carbonyl and alkoxy-carbonyl v and alkylcarbonyl-oxy substituents, and the unsaturated organic compound contains-halogen onlywhen X and Y both represent halogen, the steps of forming an equeous emulsion of said unsaturated organic compound, which emulsion contains, as ingredients of the emulsion, nitric acid in amount sufilcient to reduce the pH valueof the emulsion to between 1.5 and 3, a ferric compound in amount such that its iron content corresponds to between 0.0001 and 0.05 per cent of the weight of the unsaturated organic compound, between 0.002 and 0.2 mole of hydrogen peroxide per mole of the unsaturated organic compound, and an emulsifying agent, polymerizing the un saturated organic compound while in said emulsion, and thereafter precipitating and separating the polymer from the mixture.

5. In a method for polymerizing methyl methacrylate, the stepsof forming an aqueous emulsion containing, as ingredients of the emulsion, the methyl methacrylate and minor proportions of an emulsifying agent, a water-soluble acid, a, peroxide, and a ferric compound, and polymerizing the methyl methacrylate while in said emulsion.

6. In a method for polymerizing methyl methacrylate, the steps of forming an aqueous emulsion containing, as ingredients of the emulsion, the methyl methacrylate, an emulsi-. fying agent, a water-soluble acid in amount sufficient to reduce the pH value of the emulsion to below 6, a ferric compound in amount such that its iron content corresponds to between 0.0001 and 0.05 per cent of the weight of the methyl methacrylate, and between 0.002 and 0.2 mole of peroxide per mole of the methyl methacrylate. and polymerizing the latter w in said emulsion.

'I. In a method for polymerizing methyl methacrylate, the steps of forming an aqueous emulsion containing, as ingredients of the emulsion, the methyl methacrylate, an emulsifying agent, nitric acid in amount suflcient to reduce the pH value of the emulsion to between-1.5 and 3, a ferric compound in amount such that its iron content corresponds to between 0.0001 and 0.05 per cent of the weight of the methyl methacrylate, and between 0.002

and 0.2 mole of hydrogen peroxide per mole of the methyl methacrylate, polymerizing the latter while in said emulsion, and thereafter precip itating and separating the polymer from the 8. In a method for polymerizing a vinylidene halide, the steps of forming an aqueous emulsion containing, as ingredients of the emulsion.

the vinylidene halide and minor proportions of an emulsifying agent, a water-soluble acid. a

peroxide, and a ferric compound, and polymerising the vinylidene halide while in said emulsion.

9. In a method for polymerizing vinylidene chloride, the steps of forming an aqueous emulsion containing, as ingredients of the emulsion,

the vinylidene chloride, an emulsifying agent, a water-soluble acid in amount sufficient to reduce the pH value of the emulsion to below 6, a ferric compound in-amount such that its iron 'content corresponds to between 0.0001 and 0.05

per cent of the weight of the vinylidene chloride, 1

content corresponds to between 0.0001 and 0.05 per cent of the weight of the vinylidene chloride, and between 0.002 and 0.2 mole of hydrogen peroxideper mole of thevinylidene chloride, polymerising'the latter while in said emulsion and thereafter precipitating and separating the polymer from the mixture.

11. In a method for polymerizing a vinyl ester of an aliphatic carbowlic acid, the steps of forming an aqueous emulsion containing, as ingredients of the emulsion, said vinyl ester and minor proportionaof an emulsifying agent, a water-soluble acid, a peroxide, and a ferric compound, and polymerizing the vinyl ester while in said emulsion.

12. In a method for polymerizing vinyl acetate, the steps of forming an aqueous emulsion I containing, as ingredients of the emulsion, the

vinyl acetate, an emulsifying agent, a watersoluble acid in amount suilicient to reduce the pH. value of the emulsion to below 6, a ferric compound in amount such that its iron content corresponds to between 0.0001 and 0.05 per cent of the weight of the vinyl acetate, and between 5 0.002 and 0.2 mole of hydrogen peroxide per mole of the vinyi'acetate, and polymerizing the latter while in said emulsion.

13. In a method for polymerizing vinyl acetate, the steps of forming an aqueous emulsion containing, as ingredients of the emulsion, the

vinyl acetate, an emulsifying agent, acetic acid in amount sumcient to reduce the pH value of the emulsion to between 1.5 and 8, a ferriccompound in amount such that its iron content corresponds to between 0.0001 and 0.05 per cent of the weight of the vinyl acetate, and between 0.002 and 0.2 mole ofhydrogen peroxide per mole of the vinyl acetate, polymerizing the latter while in said emulsion. and thereafter precipitating and separating the polymer from the mixture.

. EDGAR C. BRI'I'I'ON.

WALTER. J. Ll FEVRE. 

